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Cardiovascular > Cardiac Cycle and Special Circulations > Flashcards

Cardiac Cycle and Special Circulations Flashcards

1
Q

when do heart valves produce a sound

A

when they shut

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2
Q

what is the blood flow across the heart

A

SVC-RA-TV-RV-PV-PA-PV-LA-MV-LV-AV-A

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3
Q

what triggers the recurring cardiac cycleof atrial and ventricular contractions and relaxations

A

the orderly depolarisation/ repolarisation sequence

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4
Q

what is the cardiac cycle composed of

A

all events from one heart beat to the next

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5
Q

describe heart in diastole

A

heart ventricle are relaxed and fill with blood

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6
Q

describe the heart in systole

A

heart ventricles contract and pump blood into the aorta (LV) and pulmonary artery (RV)

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7
Q

which side of the heart has a lower pressure

A

left

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8
Q

what are the 5 main events during the cardiac cycle

A

passive filling, atrial contraction, isovolumetric contraction, ventricular ejection, isovolumetric ventricular relaxation

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9
Q

after what does the valve close and why

A

Isovolumetric ventricular Contraction- so volume of blood stays the same

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10
Q

what happens to the mitral valves during ventricular ejection

A

stays closed as blood is ejected into aorta

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11
Q

what happens to the valves during isovolumetric relaxation

A

both closed and ventricle relaxes around volume of blood

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12
Q

what allows passive filling

A

pressure gradient between artia and ventricle (both close to 0)

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13
Q

what fills majority of ventricle

A

80% passive filling, 20% contraction

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14
Q

what does the P wave in the ECG signal

A

atrial depolarisation

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15
Q

when does the artria contract in the ECG

A

between the P wave and QRS

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16
Q

what completes the end diastolic volume

A

atrial contraction

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17
Q

when does ventricular contraction start in the ECG

A

after the QRS (signals ventricular depolarisation)

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18
Q

what causes the AV valves to shut

A

when the ventricular pressure exceeds the atrial pressure

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19
Q

what causes the LUB sound

A

AV valve shutting

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20
Q

describe isovolumetric contraction

A

tension rises around a closed volume

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21
Q

when does the aortic/pulmonary valve open causing ventricular ejection

A

when ventricular pressure exceeds aorta/pulmonary artery pressure

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22
Q

what does the T wave on the ECG signal

A

ventricular repolarisation

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23
Q

what happens to the ventricles after the T wave

A

relax and the ventricular pressure starts to fall

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24
Q

when do the aortic/ pulmonary valves shut after ventricular ejection

A

when ventricular pressure falls below aortic / pulmonary pressure

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25
what produces the secondary heart sound (DUB)
closure of aortic/ pulmonary valves after ventricular ejection
26
what does the valve vibration produce in the aortic pressure curve
dicrotic notch
27
what does closure of aortic/and pulmonary valves signals the start of
isovolumetric ventricular relaxation
28
describe the AV valves during isovolumetric ventricular relaxation
shur, tension falls around a closed volume
29
when do AV valves reopen after isovolumetric ventricular relaxation
When the ventricular pressure falls below atrial pressure
30
what does the first heart sound signal the beginning of
systole
31
what does the second heart sound signal the beginning of
diastole
32
why does arterial pressure never fall to zero
as arteries stretch and recoil
33
when does the JVP occur
after right atrial pressure waves
34
what type of pulse is JVP
wave pulse
35
where do the coronary arteries arise from
the base of the aorta
36
where does the majority of the venous blood drain from the heart into and via what
goes into right atrium via coronary sinus
37
what are the special adaptations of the coronary circulation
high capillary density high basal blood flow high oxygen extraction under resting conditions
38
what does the high level of oxygen extraction by the myocardium mean for changes in oxygen requirements
only way to increase oxygen supply to heart is to increase coronary blood flow
39
what controls coronary blood flow
intrinsic and extrinsic mechanisms
40
how do intrinsic mechanisms control coronary blood flow
decrease PO2 causes vasodilatation of coronary arterioles in attempt to supply heart with more blood metabolic hyperaemia adenosine (produced from breakdown of ATP) is a potent vasodilator
41
what intrinsic mechanisms control coronary blood flow
supplied by sympathetic vasoconstrictors BUT over ridden by metabolic hyperaemia (as a result of increase HR and SV) symp stim results in coronary vasodilatation adrenaline activates beta 2 adrenergic receptors cause vasodilatation and increased blood supply
42
what does stimulation of alpha receptors do
vasoconstriction
43
what what stimulation of beta 2 receptors do
vasodilatation
44
what stimulates beta 2 receptors
circulating adrenaline
45
how does decreased PO2 affect adenonsine and therefore coronary blood flow
increases adenosine and increases blood flow
46
how does an increase of metabolites affect coronary blood flow (K+, PCO2, H+)
increases blood flow
47
when does peak left coronary flow occurs and why
diastole During contraction of the ventricular myocardium (systole), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high ventricular pressures. This compression results in momentary retrograde blood flow (i.e., blood flows backward toward the aorta) which further inhibits perfusion of myocardium during systole
48
what happens to blood supply to the heart if you shorten diastole
decreases, coronary blood flow highest in diastole
49
why are the right coronary arteries less affected by contractions of the ventricles/ atrium
as right side doesn't contract as much
50
when does most myocardial perfusion occur
in diastole when the subendocardial vessels from the left coronary artery are not compressed
51
what arteries supply the brain
internal carotids and vertebral arteries
52
what happens if the grey matter of the brain is starved of oxygen
consciousness lost after few seconds of ischaemia, irreversible cell damage within ~ 3 minutes
53
what is the circle of willis
basilar (2 vertebral arteries) and carotid arteries anastomose to form circle of willis (vessel ring at base of brain)
54
what arises from the circle of willis
major cerebral arteries
55
do brain arteries respond to the barorecptor reflex
not necessarily
56
what causes a stroke
interruption/ cut off of blood supply to a region of the brian
57
what do auto regulation do and in what ranges does it work
autoregulation of cerebral blood flow guards against changes in blood flow if mean arterial blood pressure changes (between 60-160mmHg)
58
does sympathetic stimulation have a big effect on cerebral blood flow
no has little effect
59
due to autoregulation what happens to resistance vessels if MABP rises
constrict to limit blood flow
60
due to autoregulation what happens to resistance vessels if MABP fall
dilate to maintain bloodflow
61
what does a MABP below 50 mmHg cause
confusion, fainting and brain damage
62
what effect does increased PCO2 have on the cerebral vessels
causes vasodilatation
63
what effect does decreased PCO2 have on the cerebral vessels
causes vasoconstriction
64
what is regional hyperaemia
blood flow increases to active parts of the brain
65
what is ICP and its normal values
intracranial pressure 8-13 mmHg
66
what is CPP and how is it calculated
cerebral perfusion pressure (MAP - ICP)
67
what effects does an increasing ICP have on CPP and cerebral blood flow
decreases CPP and cerebral blood flow
68
what can increase ICP
head injury or brain tumour
69
what is the blood brain barriers
cerebral capillaries which have very tight intercellular junctions
70
what are cerebral capillaries highly permeable to
O2 and CO2
71
how does glucose pass the BBB
by facilitated diffusion using specific carrier molecules
72
what is the BBB exceptionally impermeable to , what does this allow
hydrophilic substances such as ions, catecholamines, proteins etc helps protect brain neurones from fluctuating levels of ions etc in blood
73
how much of cardiac output travels into pulmonary circulation from the right ventricle
all of it
74
what meets the metabolic needs to the airways
systemic bronchial circulation
75
how much of systemic circulation resistance is pulmonary
about 10%
76
how does pulmonary capillary resistance compare to systemic capillary resistance
low
77
what adaptation of the pulmonary circulation helps to protect against pulmonary oedema
absorptive forces
78
what effect does hypoxia have on pulmonary arterioles
vasoconstriction- opposite so that blood is diverted away from poorly ventilated areas of lung
79
what is resting blood flow low
because of sympathetic vasoconstrictor tone
80
what overcomes sympathetic vasoconstrictor activity during activity
metabolic hyperaemia
81
what changes in the vasculature occur during exercise
blood flow to skeletal muscle increases Metabolic hyperaemia overcomes sympathetic vasoconstrictor activity Circulating adrenaline causes vasodilatation (beta2 adrenergic receptors) Plus increased cardiac output during exercise, these could increase skeletal muscle blood flow many folds
82
where do large veins in limbs lie
between skeletal muscle
83
what causes varicose veins
blood pooling in the lower limbs if venous valves become incompetent
84
why do varicose veins lead to reduce cardiac output
because of chronic compensatory increase in blood volume

Cardiovascular (34 decks)

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